1. Field of the Invention
The invention relates to a keyboard matrix scanning method, and in particular to a security keyboard matrix scanning method for preventing a third party from knowing password being input from the keyboard during a password identification operation.
2. Description of the Related Art
In line with the popularity of an information system for financial transaction or management information, demands for preventing a third party from inappropriately operating and illegally accessing the information system is becoming increasingly greater. At present, the most commonly used method to prevent illegal operations is to request the user to key in a password. However, as criminals become more sophisticated, they can easily obtain a user""s input password by monitoring and observing the input operation, and then illegally access the information systems.
FIG. 1 is a schematic drawing illustrating a conventional keyboard matrix scanning structure for password identification. As shown in FIG. 1, scanning lines of a keyboard which respectively connects to a X-port and a Y-port are typically arranged into a matrix, such as a matrix consisting of n rows and m columns of scanning lines. Each cross point corresponds to a position that one key is located and thus there are totally nxm keys. One scanning line of each key is electrically connected to the Y-port which serves as a scanning signal output port and has totally n lines. The other scanning line of each key is electrically connected to the X-port which serves as a scanning signal input port or scanning signal sensing port and has totally m lines. When a key is pressed, an electric conduction is constructed between two corresponding lines which crosses at its corresponding position, and thus a scanning signal output from a corresponding scanning signal output line of the Y-port will be sent to a corresponding scanning signal input line of the X-port, thereby the position of the key being pressed is able to be detected.
In detail, the output scanning lines Y0xcx9cYn of the Y-port are all at a high logic level and the input scanning lines X0xcx9cXm of the X-port are also at a high logic level when a scanning/detection procedure is not executed. In operation, each of the output scanning lines Y0xcx9cYn repeatedly outputs a scanning signal in sequence. That is, each of the output scanning lines Y0xcx9cYn outputs a low logic level in sequence while the else having not been selected remain a high logic level. In the meanwhile, the X-port will detect whether any one of the input scanning lines X0xcx9cXm is at a low logic level. If one of the input scanning lines of the X-port is at a low logic level, it indicates that one key on a line corresponding to that scanning lines has been pressed. Otherwise, scanning is continuously implemented. In other words, if a key Kxy is pressed, a corresponding input scanning line Xx will detect a low logic level when a corresponding output scanning line Yy outputs a low logic level signal, i.e., the output scanning line Yy and the input scanning line Xx are of a low logic level while the other output and input scanning lines are of a high logic level. According to the above manner, the keys being pressed in a keyboard would be detected by the password identification device.
Moreover, in the conventional keyboard matrix scanning method, the X-port is dedicated to serve as an input port while the Y-port is dedicated to serve as an output port. Thus, a third party can easily sense a pair of output and input scanning lines which are both at a low logic level, and knows the cross point and its corresponding key being pressed, by means of wires connected from the outside to each line and a detection to the level thereof. Thus, a user password can be obtained by a third party for illegal operations including cash withdrawals or accessing classified information.
In view of the above, an object of the invention is to provide a security keyboard matrix scanning method which is utilized in a password identification device and can efficiently prevent a third party from obtaining a user""s password or detecting the keys being pressed.
To achieve the above object, a security keyboard matrix scanning method for a keyboard in accordance with this invention utilizes bi-directional input/output ports, in which each line of the X-port and the Y-port can be selectively designated as a sensing line or an output line, to construct the X-port and Y-port such that at least one line of any one of the two ports can output a scanning signal representative of a dummy scanning signal at the time the actual scanning signal is output from another line of any one of the two ports.
In a further embodiment, the security keyboard matrix scanning method of the invention is characterized in that when at least one scanning line of the X-port functions as a sensing line for inputting at least one scanning signal output from the Y-port, at least one of the other scanning lines of the X-port functions as an output line and synchronously outputs an scanning signal serving as an interference signal or a dummy signal.
By specifying at least one scanning line of the X-port and the Y-port to output an interference signal, there will be many keys locations detected to have been pressed. The actual key being pressed could not be detected even though the scanning lines are illegally connected to the outside. As a result, it can efficiently prevent a third party from detecting the key being pressed for illegal use. Thus, the security level of the password identification device is greatly enhanced.
The invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus do not limit the present invention.